JP5121646B2 - Piezoelectric resonator - Google Patents

Description

  The present invention relates to a piezoelectric oscillator including a capacitor that constitutes an oscillation circuit, which is constituted by a pair of capacitive electrodes, and more particularly to a piezoelectric oscillator capable of adjusting the frequency in a finished product state.

  2. Description of the Related Art Conventionally, microcomputers have been widely used for communication devices and electronic devices. As a clock source for such a microcomputer, a piezoelectric resonator having a built-in capacitor for oscillation is known. This piezoelectric oscillator has a structure in which a capacitor constituting an oscillation circuit is connected between an input terminal and an output terminal of a piezoelectric element and a ground electrode.

As such a piezoelectric oscillator, a piezoelectric resonator is formed as a piezoelectric element between both vibrating electrodes by forming vibrating electrodes on both main surfaces of the piezoelectric substrate, and in the vicinity of the vibrating electrodes on both main surfaces of the piezoelectric substrate. 2. Description of the Related Art A built-in capacitor type piezoelectric resonator in which a capacitor electrode is provided and a capacitor is formed between the capacitor electrode and the vibrating electrode is known (see, for example, Patent Document 1). By adopting such a structure, it is possible to provide a piezoelectric resonator with a built-in capacitor that constitutes a Colpitts type oscillation circuit in which the oscillation frequency can be obtained relatively stably.
JP-A-3-165614

  In the piezoelectric oscillator constituting the Colpitts oscillation circuit, the accuracy of the oscillation frequency can be further improved by adjusting the variation of the built-in capacitor due to the manufacturing process from the outside. For this purpose, a method of adjusting the capacitance by deleting a part of the capacitive electrode is conceivable. However, in the case of the piezoelectric oscillator proposed in Patent Document 1, a voltage is applied to the capacitive electrodes to apply piezoelectricity between the capacitive electrodes. By changing the degree of polarization of the piezoelectric material of the substrate, the dielectric constant between the capacitive electrodes can be changed, and thereby the capacitance between the capacitive electrodes can be adjusted.

  However, in the piezoelectric resonator proposed in Patent Document 1, the capacitance that constitutes the oscillation circuit together with the piezoelectric resonator is configured using the piezoelectric material as a dielectric, and by changing the degree of polarization of the piezoelectric material Although it is possible to adjust the capacitance between the capacitance electrodes, the capacitance is formed by forming the capacitance electrode on the same piezoelectric substrate as the piezoelectric resonator. If the degree of polarization is changed, the capacitive electrode and the vibrating electrode of the piezoelectric resonator are close to each other. Therefore, even if the degree of polarization is changed only between the capacitive electrodes, the change in the degree of polarization is only between the capacitive electrodes. In addition, there is a problem that the degree of polarization of the piezoelectric resonator also changes. For this reason, if the degree of polarization between the vibrating electrodes constituting the piezoelectric resonator changes, the oscillation frequency changes greatly. Therefore, high-accuracy frequency adjustment cannot be performed, and the accuracy of the oscillation frequency of the piezoelectric resonator is increased. There was a problem that was difficult.

  In addition, the piezoelectric oscillator proposed in Patent Document 1 can be adjusted by shaving the piezoelectric substrate for frequency adjustment and changing the thickness of the piezoelectric substrate. When the thickness is changed, the capacitance also changes, which makes it difficult to adjust the frequency of the piezoelectric oscillator with high accuracy.

  The present invention has been devised in view of the problems in such a conventional piezoelectric resonator, and its purpose is to adjust the built-in capacitance without affecting the characteristics of the piezoelectric resonator. Accordingly, it is an object of the present invention to provide a piezoelectric resonator capable of adjusting the oscillation frequency and having high oscillation frequency accuracy.

The piezoelectric resonator of the present invention includes a piezoelectric element in which a first vibration electrode and a second vibration electrode facing each other with the first piezoelectric substrate sandwiched between the surface of the first piezoelectric substrate and a second piezoelectric substrate. A first capacitor electrode and a second capacitor electrode are respectively deposited on one main surface, and a ground for forming a capacitor between the first capacitor electrode and the second capacitor electrode on one or the other main surface. A capacitive substrate having electrodes attached thereto, and the piezoelectric element is disposed with a space for vibration around the capacitive substrate, and the first capacitive electrode and the first vibrating electrode are And the second capacitor electrode and the second vibrating electrode are electrically connected ,
Wherein said second piezoelectric substrate between the first capacitor electrode and the second capacitor electrode and the ground electrode is one which is characterized that you have been capacitor is polarized is formed.

  In the piezoelectric resonator according to the aspect of the invention, the ground electrode may be attached to the other main surface of the second piezoelectric substrate so as to face the first capacitor electrode and the second capacitor electrode. It is characterized by being.

  The piezoelectric resonator according to the present invention is characterized in that, in the above configuration, the piezoelectric element is mounted on one main surface of the capacitive substrate via a conductive connecting material.

  Furthermore, the piezoelectric resonator of the present invention has the above-described configuration, and the second main surface of the second piezoelectric substrate is electrically connected to the first mounting electrode and the second capacitance electrode electrically connected to the first capacitance electrode. The second mounting electrodes connected to each other are attached.

  Furthermore, the piezoelectric resonator of the present invention is characterized in that, in the above-described configuration, the first piezoelectric substrate and the second piezoelectric substrate are made of the same ferroelectric material.

  In the piezoelectric oscillator according to the aspect of the invention, in the above configuration, the second piezoelectric substrate is formed by laminating two piezoelectric layers, and the ground is attached to the first capacitor electrode and the other main surface. An internal electrode electrically isolated between the piezoelectric layers is disposed in a region facing the electrode and a region facing the second capacitor electrode and the ground electrode deposited on the other main surface, The polarization directions of the upper and lower piezoelectric layers with the internal electrode as a boundary are opposite to each other.

  In the piezoelectric resonator according to the aspect of the invention, in the configuration described above, the ground electrode is attached between the first capacitor electrode and the second capacitor electrode on one main surface of the second piezoelectric substrate. The polarization direction of the second piezoelectric substrate is opposite between the first capacitor electrode and the ground electrode and between the second capacitor electrode and the ground electrode.

  According to the piezoelectric resonator of the present invention, the piezoelectric element in which the first vibration electrode and the second vibration electrode facing each other with the first piezoelectric substrate interposed therebetween are attached to the surface of the first piezoelectric substrate, and the second piezoelectric substrate A first capacitor electrode and a second capacitor electrode are respectively deposited on one main surface of the first electrode, and a capacitor is formed on one or the other main surface between the first capacitor electrode and the second capacitor electrode. A capacitive substrate to which a ground electrode is attached, and the piezoelectric element is disposed with a space for vibration around the capacitive substrate, and the first capacitive electrode and the first vibrating electrode, Since the second capacitor electrode and the second vibrating electrode are electrically connected to each other, the first vibrating electrode and the second vibrating electrode respectively connected to the input side terminal and the output side terminal of the piezoelectric element. Are maintained at the same potential while the first capacitor electrode and the capacitor substrate Since a voltage can be applied between the second capacitor electrode and the ground electrode, and the first piezoelectric substrate of the piezoelectric element and the second piezoelectric substrate of the capacitor portion forming the capacitor are separate substrates, the piezoelectric element The capacitance can be adjusted by changing the dielectric constant and changing the degree of polarization of the piezoelectric material of the capacitive substrate without affecting the degree of polarization of the piezoelectric material by applying voltage. The oscillation frequency of the piezoelectric resonator can be adjusted without changing the extreme and without affecting the characteristics of the piezoelectric element.

  According to the piezoelectric oscillator of the present invention, when the ground electrode is attached to the other main surface of the second piezoelectric substrate so as to straddle the first capacitor electrode and the second capacitor electrode, While a capacitor is formed between the first capacitor electrode and the second capacitor electrode and the ground electrode, a ground electrode formed with a relatively large area can be used as a mounting electrode, so that mounting with sufficient strength is possible. It becomes easy.

  Further, according to the piezoelectric oscillator of the present invention, when the piezoelectric element is mounted on one main surface of the capacitive substrate via the conductive connecting material, the capacitive substrate and the piezoelectric element are connected via the conductive connecting material. Thus, a space required for vibration of the piezoelectric element can be secured between them, and the mounting area of the piezoelectric element can be reduced, so that further miniaturization is possible.

  According to the piezoelectric oscillator of the present invention, the other main surface of the second piezoelectric substrate is electrically connected to the first mounting electrode and the second capacitance electrode that are electrically connected to the first capacitance electrode. When the second mounting electrode is attached, it can be surface-mounted by the first mounting electrode and the second mounting electrode without using wire bonding or the like when mounting the piezoelectric oscillator. It is possible to simplify the manufacturing process of an electronic circuit, a circuit module, and the like on which the oscillator is mounted.

  In addition, since the second piezoelectric substrate can be surface-mounted on the mounting substrate, the second piezoelectric substrate is firmly fixed on the mounting substrate, which is caused by using a piezoelectric material for the second piezoelectric substrate. Piezoelectric vibrations of the second piezoelectric substrate can be kept small. Accordingly, it is possible to suppress abnormal oscillation of the piezoelectric oscillator that occurs when the piezoelectric vibration generated in the capacitive substrate overlaps the piezoelectric vibration generated in the piezoelectric element.

  According to the piezoelectric resonator of the present invention, when the first piezoelectric substrate and the second piezoelectric substrate are made of the same ferroelectric material, the thermal expansion coefficients of the first piezoelectric substrate and the second piezoelectric substrate are equal, Even if the first piezoelectric substrate and the second piezoelectric substrate expand / contract due to changes in the amount of heat applied to the first piezoelectric substrate and the second piezoelectric substrate, the expansion / contraction amounts between the first piezoelectric substrate and the second piezoelectric substrate are equal, Since the thermal stress between the first piezoelectric substrate and the second piezoelectric substrate can be kept small, damage due to thermal stress is reduced as compared with the case where different ferroelectric materials are used for the first piezoelectric substrate and the second piezoelectric substrate. A piezoelectric oscillator with less reliability and high reliability.

  Further, according to the piezoelectric oscillator of the present invention, the second piezoelectric substrate is formed by laminating two piezoelectric layers, and the opposing region between the first capacitive electrode and the ground electrode attached to the other main surface An internal electrode electrically isolated between the piezoelectric layers is disposed in a region facing the second capacitor electrode and the ground electrode deposited on the other main surface. When the polarization direction of the piezoelectric layer is opposite, the second piezoelectric substrate when the potential difference is generated between the first capacitor electrode and the ground electrode and between the second capacitor electrode and the ground electrode is the second piezoelectric substrate. When one of the two piezoelectric layers of the substrate is expanded, the other is contracted, and the change in thickness of each of the two piezoelectric layers is offset, and the overall change in thickness is reduced. To suppress the piezoelectric vibration of the second piezoelectric substrate Kill. Thereby, generation | occurrence | production of the unnecessary peak other than the desired frequency in a frequency-impedance characteristic by the piezoelectric vibration of a 2nd piezoelectric substrate can be suppressed.

  According to the piezoelectric oscillator of the present invention, the ground electrode is attached between the first capacitor electrode and the second capacitor electrode on one main surface of the second piezoelectric substrate, and the second piezoelectric substrate When the polarization direction is reverse between the first capacitor electrode and the ground electrode and between the second capacitor electrode and the ground electrode, the first capacitor electrode and the second capacitor electrode are excited to excite the first piezoelectric substrate. When the voltage is applied between the first and second piezoelectric substrates, one of the first capacitor electrode and the ground electrode of the piezoelectric layer of the second piezoelectric substrate extends between the second capacitor electrode and the ground electrode. When the other side contracts, the amount of change in the direction parallel to the piezoelectric layer is canceled out and the change in the direction parallel to the piezoelectric layer is reduced as a whole, so that the piezoelectric vibration of the second piezoelectric substrate is reduced. Can be suppressed. Thereby, generation | occurrence | production of the unnecessary peak other than the desired frequency in a frequency-impedance characteristic by the piezoelectric vibration of a 2nd piezoelectric substrate can be suppressed.

  Hereinafter, the piezoelectric resonator of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view showing an example of an embodiment of the piezoelectric oscillator of the present invention, and FIG. 2 is a cross-sectional view taken along line A-A 'of the piezoelectric oscillator 10 of FIG.

  The piezoelectric resonator 10 shown in these drawings has a basic configuration in which the piezoelectric element 1 mounted on the capacitive substrate 2 is attached to the capacitive substrate 2 so as to cover the capacitive substrate 2 and the piezoelectric element 1. 3 is sealed.

  The piezoelectric element 1 is configured, for example, by attaching a first vibration electrode 1a and a second vibration electrode 1b to the upper and lower surfaces of a first piezoelectric substrate 1c. The first piezoelectric substrate 1c is formed, for example, as a rectangular flat plate having a length of about 0.4 mm to 4 mm, a width of about 0.2 mm to 3 mm, and a thickness of about 40 μm to 1 mm, and has a thickness direction, a width direction, or a length direction. Are polarized. Examples of the material of the first piezoelectric substrate 1c include piezoelectric ceramics based on lead titanate, lead zirconate titanate, sodium niobate, potassium niobate, bismuth layered compounds, crystal, lithium tantalate, niobium, and the like. It can be formed using a piezoelectric single crystal such as lithium acid.

  In this example, the first vibration electrode 1a is formed in a region extending from the central portion of the upper surface of the first piezoelectric substrate 1c to one end portion, and the second vibration electrode 1b is formed in the first piezoelectric substrate 1c in this example. It is formed in a region extending from the central portion of the lower surface of the other end to the other end. As a material of the first vibrating electrode 1a and the second vibrating electrode 1b, for example, a metal such as gold, silver, copper, and aluminum can be used, and a thickness of about 0.1 μm to 3 μm is formed on the surface of the first piezoelectric substrate 1c. To be attached. In such a piezoelectric element 1, when a voltage is applied between the first vibrating electrode 1a and the second vibrating electrode 1b from both ends, the piezoelectric element 1 has a specific area in a region where the first vibrating electrode 1a and the second vibrating electrode 1b face each other. A piezoelectric vibration of thickness longitudinal vibration or thickness shear vibration is generated at a frequency.

  The case 3 has a function of protecting the piezoelectric element 1 housed in the space formed together with the capacitor substrate 2 from the physical and chemical influences from the outside, water in the space formed together with the capacitor substrate 2, etc. It has a hermetic sealing function to prevent foreign material from entering. As a material of such a case 3, for example, resin, glass, ceramics, or the like can be used. In the piezoelectric resonator 10 of the present invention, an insulating resin material such as an epoxy resin is used for the case 3, and further, an inorganic filler is contained in a proportion of 25 to 80% by mass and thermal expansion with the capacitor substrate 2 is performed. Reliability is improved by reducing the difference between the coefficients and reducing the difference in thermal expansion / contraction between the case 3 and the capacitor substrate 2 due to temperature change.

  Next, FIG. 3A is an external perspective view of the case 3 of the piezoelectric oscillator 10 of FIG. 1 viewed from below, and FIG. 3B is a state in which the case 3 is removed from the piezoelectric oscillator 10 of FIG. FIG. As shown in FIGS. 2 and 3 (b), in the piezoelectric resonator 10 of this example, the above-described piezoelectric element 1 is a capacitive substrate using the conductive connecting members 7a and 7b formed at both ends. 2 is electrically connected to and fixed to the first capacitor electrode 2a and the second capacitor electrode 2b formed on the upper surface of the second electrode.

  The conductive connecting members 7 a and 7 b have a function of securing a predetermined space (gap) between the upper surface of the capacitive substrate 2 and the piezoelectric element 1 by being interposed between the capacitive substrate 2 and the piezoelectric element 1. doing. As such conductive connection materials 7a and 7b, for example, solder, conductive adhesive, or the like is used. For example, in the case of solder, a solder material that does not contain lead made of copper, tin, or silver is used. In the case of a conductive adhesive, an epoxy-based conductive resin containing 75 to 95% by mass of conductive particles such as silver, copper and nickel is used. Moreover, from the point which is excellent in elasticity, the conductive resin etc. which consist of silicone resin are used suitably.

  The capacitor substrate 2 has a first capacitor electrode 2a and a second capacitor electrode 2b attached to one main surface (the upper surface in this example) of the second piezoelectric substrate 2c, respectively, and the other main surface of the second piezoelectric substrate 2c ( In this example, the lower surface) has a structure in which a ground electrode 6 facing the first capacitor electrode 2a and the second capacitor electrode 2b is attached.

  When the first capacitor electrode 2a and the second capacitor electrode 2b and the ground electrode 6 are opposed to each other through the second piezoelectric substrate 2c as in the present example, the region where the first capacitor electrode 2a and the ground electrode 6 are opposed to the first electrode By setting the areas where the two-capacitance electrodes 2b and the ground electrode 6 are opposed to each other, the capacitances obtained in the opposed areas are equalized. When the first capacitor electrode 2a and the second capacitor electrode 2b and the ground electrode 6 are opposed to each other via the second piezoelectric substrate 2c, the region where the first capacitor electrode 2a and the ground electrode 6 are opposed to the second capacitor electrode Since the region where 2b and the ground electrode 6 are opposed can be increased, the capacitance can be increased. It should be noted that the capacitance obtained in each of the opposing regions is determined by the characteristics of the amplifier circuit element that is connected to the piezoelectric oscillator 10 and constitutes an oscillation circuit.

  The first capacitor electrode 2a and the second capacitor electrode 2b are provided with a capacitor forming portion 2e extending from the side portion on the center side of the first capacitor electrode 2a and the second capacitor electrode 2b toward the center portion of the capacitor substrate 2. The capacitance forming portion 2e is configured to obtain a capacitance between the capacitance forming portion 2e and the ground electrode 6 having the ground potential formed at the center of the lower surface of the capacitance substrate 2. The ground electrode 6 having this ground potential is electrically connected to the side ground electrode 6a formed on the side of the capacitor substrate 2 so as to reach the side surface of the second piezoelectric substrate 2c and extend in the thickness direction. Yes.

  FIG. 4 is an equivalent circuit diagram of the piezoelectric resonator 10 of this example. As shown in FIG. 4, the piezoelectric resonator 10 of this example has a piezoelectric element 1 in which a capacitive element in which a capacitance is formed between the capacitive substrate 2 and the ground is connected to both ends of the piezoelectric element 1 (piezoelectric resonator). A resonance circuit is configured, and for example, an oscillation component used for a clock source of a microcomputer used in communication equipment and electronic equipment can be used.

  In the piezoelectric resonator 10 of this example, the second piezoelectric substrate 2c constituting the capacitor substrate 2 has, for example, a length of about 0.6 mm to 5 mm, a width of about 0.5 mm to 4 mm, and a thickness of about 0.05 mm to 1 mm. A substrate having a high dielectric constant, formed as a rectangular flat plate. The material of the second piezoelectric substrate 2c can be, for example, piezoelectric ceramics that are polarized using a lead zirconate titanate, sodium niobate, potassium niobate, bismuth layered compound, or the like as a base material.

  In the piezoelectric resonator 10 of this example, the first capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6 have the ground electrode 6 on the other main surface of the second piezoelectric substrate 2c and the first capacitor electrode 2a. The two capacitor electrodes 2b are attached to face each other. By forming the first capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6 in this manner, the necessary capacitance is formed between the first capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6. The ground electrode 6 formed with a relatively large area on the other main surface (lower surface) of the second piezoelectric substrate 2c can be used as an electrode for mounting, and is a piezoelectric that is easy to mount firmly with sufficient strength. It becomes the oscillator 10.

  The first capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6 may be made of conductive resin in which metal powder such as gold, silver, copper, or aluminum is dispersed in resin, or such metal powder. A thick film conductor or the like baked by adding an additive such as glass can be used. For example, a conductive resin paste in which a metal powder such as gold, silver, copper, nickel or the like is dispersed in an epoxy resin as a conductive filler is prepared, and this conductive resin paste is applied to the second piezoelectric substrate 2c. It can be formed by applying the resin to a predetermined part of the upper and lower surfaces using, for example, a screen printing method or a roller transfer method, and then curing the resin by heating or ultraviolet irradiation.

  According to the piezoelectric resonator 10 of this example, the piezoelectric element 1 is formed by attaching the first vibration electrode 1a and the second vibration electrode 1b facing each other with the first piezoelectric substrate 1c sandwiched on the surface of the first piezoelectric substrate 1c. The first capacitive electrode 2a and the second capacitive electrode 2b are respectively deposited on one main surface of the second piezoelectric substrate 2c, and between the first capacitive electrode 2a and the second capacitive electrode 2b on the other main surface. And a capacitor substrate 2 to which a ground electrode 6 for forming a capacitor is attached, and the piezoelectric element 1 is mounted on the capacitor substrate 2 via the conductive connecting members 7a and 7b, thereby being attached to the capacitor substrate 2. The piezoelectric element 1 is arranged with a space for vibration around it, and the first capacitive electrode 2a and the first vibrating electrode 1a are connected via the conductive connecting material 7a and the second capacitive electrode 2b and the second The two vibrating electrodes 1b are electrically connected to each other through the conductive connecting material 7b. Therefore, the input side terminal (for example, the first vibration electrode 1a) and the output side terminal (for example, the second vibration electrode 1b) of the piezoelectric element 1 are kept at the same potential, while the capacitance substrate 2 Since a voltage can be applied so that a potential difference is generated between the first capacitor electrode 2a and the second capacitor electrode 2b and the ground electrode 6, the degree of polarization of the piezoelectric material of the first piezoelectric substrate 1c of the piezoelectric element 1 is affected. Without changing the degree of polarization, the first capacitor electrode 2a and the second capacitor electrode 2b in the capacitor substrate 2 and the ground electrode 6 can change the degree of polarization to the piezoelectric material of the second piezoelectric substrate 2c having only the capacitor forming portion 2e. Therefore, it is possible to change the capacitance value by changing the dielectric constant by changing the degree of polarization of the capacitance forming portion 2e, and thereby the oscillation of the piezoelectric oscillator 10 without changing the characteristics of the piezoelectric element 1. Frequency It can be an integer.

  Further, according to the piezoelectric resonator 10 of this example, when the piezoelectric element 1 is mounted on one main surface of the capacitive substrate 2 via the conductive connecting materials 7a and 7b, the capacitive substrate 2 and the piezoelectric element 1 are connected. Since the conductive connecting members 7a and 7b can be stacked and integrated with a minute gap and a space for vibrations secured, the mounting area of the piezoelectric element 1 can be reduced and efficient. Miniaturization is possible.

  In the piezoelectric oscillator 10 of this example, as a structure for electrically connecting the piezoelectric element 1 and the capacitor substrate 2 without using the conductive connection members 7a and 7b, for example, the second vibrating electrode 1b is the first. The first piezoelectric substrate 1c is formed so as to wrap around the upper surface of the end portion of the piezoelectric substrate 1c, and both end portions of the lower surface of the first piezoelectric substrate 1c are fixed to the upper surface of the capacitor substrate 2 with an insulating bonding member. There is a structure in which the first vibrating electrode 1a and the second vibrating electrode 1b on the upper surface of the first electrode are connected to the first capacitor electrode 2a and the second capacitor electrode 2b by wire bonding.

  Further, according to the piezoelectric oscillator 10 of the present example, when the first piezoelectric substrate 1c and the second piezoelectric substrate 2c are made of the same ferroelectric material, the thermal expansion coefficients of the first piezoelectric substrate 1c and the second piezoelectric substrate 2c. Even if the first piezoelectric substrate 1c and the second piezoelectric substrate 2c expand / contract due to changes in the amount of heat applied to the first piezoelectric substrate 1c and the second piezoelectric substrate 2c, the expansion amount between the piezoelectric substrates 1c and 2c Since the shrinkage amount becomes equal and the stress between the first piezoelectric substrate 1c and the second piezoelectric substrate 2c can be kept small, different ferroelectric materials are used for the first piezoelectric substrate 1c and the second piezoelectric substrate 2c. Compared to the case, the piezoelectric oscillator 10 is less reliable due to thermal history and has high reliability.

  In this way, the first piezoelectric substrate 1c and the second piezoelectric substrate 2c are made of the same ferroelectric material (piezoelectric material), and the thermal expansion coefficients of the first piezoelectric substrate 1c and the second piezoelectric substrate 2c are made equal, In the case where the reliability is high and the resonance characteristics in the high frequency region are important, the first piezoelectric substrate 1c is preferably lead titanate (PT) which is excellent in the resonance characteristics in the high frequency region, and the second piezoelectric substrate 2c is also made of titanium. Lead acid (PT) is used. By using the same ferroelectric material for the first piezoelectric substrate 1c and the second piezoelectric substrate 2c, the stress generated by the thermal history between the first piezoelectric substrate 1c and the second piezoelectric substrate 2c can be kept small. .

  If the capacitor substrate 2 requires high capacitance, for example, the first piezoelectric substrate 1c is made of lead titanate (PT), which is a material having excellent resonance characteristics in a high frequency region, and the second piezoelectric substrate. For 2c, it is appropriate to use a ferroelectric material such as lead zirconate titanate (PZT) having a high relative dielectric constant.

  In the piezoelectric resonator 10 of this example, the first capacitor electrode 2a and the second capacitor electrode 2b formed on the upper surface of the second piezoelectric substrate 2c are each extended to reach the side surface of the second piezoelectric substrate 2c with the shortest distance. A protruding portion 2 d is provided, and the extending portion 2 d is electrically connected to an input / output terminal electrode 2 f formed on the side surface of the capacitor substrate 2. As a result, the first capacitive electrode 2a formed on the upper surface of the second piezoelectric substrate 2c is connected to the first mounting electrode formed on the lower surface of the second piezoelectric substrate 2c via the extending portion 2d and the input / output terminal electrode 2f. 4 is formed on the lower surface of the second piezoelectric substrate 2c via the extended portion 2d and the input / output terminal electrode 2f. Since the second mounting electrode 5 is connected with the shortest distance, the first capacitor electrode 2a and the first mounting electrode 4 and the second capacitor electrode 2b and the second mounting electrode 5 are respectively low in inductance and low resistance. Can be connected. Further, when mounting the piezoelectric oscillator 10 configured as described above, the piezoelectric oscillator 10 can be surface-mounted by the first mounting electrode 4 and the second mounting electrode 5 without using wire bonding or the like. The manufacturing process of an electronic circuit, a circuit module, etc. for mounting can be simplified.

  The first mounting electrode 4 is attached to the lower surface of the capacitor substrate 2 so as to be located in a region substantially opposite to the extending portion 2d of the first capacitor electrode 2a with the second piezoelectric substrate 2c interposed therebetween. The first capacitor electrode 2a is electrically connected via an input / output terminal electrode 2f and an extension 2d formed on the side surface of the capacitor substrate 2 so as to extend in the thickness direction of the capacitor substrate 2.

  The second mounting electrode 5 is attached to the lower surface of the capacitor substrate 2 so as to be positioned in a region substantially opposite to the extending portion 2d of the second capacitor electrode 2b with the second piezoelectric substrate 2c interposed therebetween. The second capacitor electrode 2b is electrically connected via an input / output terminal electrode 2f and an extension 2d formed on the side surface of the capacitor substrate 2 so as to extend in the thickness direction of the capacitor substrate 2.

  According to the piezoelectric oscillator 10 of the present example, the first mounting electrode 4 and the second capacitor electrically connected to the first capacitor electrode 2a are thus formed on the other main surface (lower surface) of the second piezoelectric substrate 2c. Since the second mounting electrode 5 electrically connected to the electrode 2b is attached, when the piezoelectric oscillator 10 is mounted on a mounting board such as a circuit board, for electrical connection with the mounting board or the like Since the surface mounting can be performed by the first mounting electrode 4 and the second mounting electrode 5 without using wire bonding or the like, the manufacturing process of an electronic circuit, a circuit module or the like for mounting the piezoelectric oscillator 10 can be simplified. Further, when surface mounting is performed on the mounting substrate by the first mounting electrode 4 and the second mounting electrode 5 and the ground electrode 6 formed on the other main surface (lower surface) of the second piezoelectric substrate 2c, Since it is firmly fixed on the substrate, the piezoelectric vibration generated by using the piezoelectric material for the second piezoelectric substrate 2c can be suppressed to be small. Thereby, even when the piezoelectric vibration generated in the capacitive substrate 2 overlaps the piezoelectric vibration generated in the piezoelectric element 1, the abnormal oscillation of the piezoelectric oscillator 10 can be suppressed.

  The first mounting electrode 4, the second mounting electrode 5 and the ground electrode 6 formed on the lower surface of the capacitor substrate 2 (second piezoelectric substrate 2 c) are external circuits, particularly when formed using a conductive resin. Since the stress applied to the capacitor substrate 2 from the circuit substrate or the like constituting the capacitor can be relaxed by these electrodes and the capacitor substrate 2 can be protected from accidental destruction, it is preferable in terms of reliability.

  The piezoelectric oscillator of the present invention as described above can be manufactured by the following method, for example.

  In the first step, the piezoelectric element 1 and the capacitor substrate 2 are prepared.

  The first piezoelectric substrate 1c and the second piezoelectric substrate 2c are formed by, for example, a method of pressing a raw material powder by adding a binder, or mixing the raw material powder with water and a dispersant using a ball mill and then drying the binder, solvent, plastic After forming a substrate by baking at a peak temperature of about 1100 ° C. to 1400 ° C. to form a green sheet by a method such as molding using a doctor blade by adding an agent, etc., the temperature is about 25 ° C. to 200 ° C. Then, it is formed by applying a voltage of about 1 kV / mm to 6 kV / mm in the thickness direction and performing a polarization treatment.

  The first vibrating electrode 1a and the second vibrating electrode 1b formed on the upper and lower surfaces of the first piezoelectric substrate 1c are made of metal on the upper and lower surfaces of the first piezoelectric substrate 1c using, for example, a vacuum deposition method, a PVD method, a sputtering method, or the like. A film is deposited, a photoresist film having a thickness of about 1 μm to 10 μm is formed on each metal film using a spin coat method or the like, and then patterned by photoetching, whereby the upper and lower surfaces of the first piezoelectric substrate 1c are formed. To form. Thus, the piezoelectric element 1 is prepared and prepared.

  If the first capacitor electrode 2a, the second capacitor electrode 2b, the first mounting electrode 4, the second mounting electrode 5, and the ground electrode 6 are made of conductive resin, for example, silver, copper, nickel as the conductive filler A conductive resin paste in which a metal powder such as 75% to 95% by mass is dispersed in an epoxy resin is prepared, and this conductive resin paste has a predetermined upper and lower surfaces with respect to the second piezoelectric substrate 2c. It can be formed by curing the resin by heating or ultraviolet irradiation after coating on this part using, for example, a screen printing method or a roller transfer method. The thickness of these electrodes may be, for example, about 10 μm to 60 μm. In order to improve solderability, a plating film may be deposited on the surfaces of these electrodes using copper, nickel, tin, gold or the like. The capacitor substrate 2 is prepared and prepared as described above.

  In the next step, the piezoelectric element 1 is mounted on the capacitor substrate 2 using the conductive connection members 7a and 7b made of a conductive adhesive.

  The conductive connecting materials 7a and 7b are coated on the first capacitor electrode 2a and the second capacitor electrode 2b by using an adhesive formed by dispersing metal powder in a resin and using a dispenser or the like. The first vibration electrode 1a is connected to the conductive connection material 7a on the first capacitance electrode 2a, and the second vibration electrode 1b is connected to the conductive connection material 7b on the second capacitance electrode 2b. Then, the piezoelectric element 1 is placed, and the resin of the conductive adhesive is cured by heating or ultraviolet irradiation. At this time, in a state before the conductive adhesive is cured, the conductive connection members 7a and 7b wrap around from the lower surface side of the first piezoelectric substrate 1c to the upper surface side at the respective end portions of the piezoelectric element 1. Thus, the conductive connecting material 7a can be electrically connected to the first vibrating electrode 1a, and the conductive connecting material 7b can be reliably electrically connected to the second vibrating electrode 1b.

  In the next step, the opening peripheral surface 3 b of the lower recess 3 a of the case 3 is joined to the upper surface of the capacitor substrate 2 so as to cover the piezoelectric element 1.

  The case 3 is prepared and prepared in advance by injection molding of a thermosetting resin in which an inorganic filler is dispersed in a resin. A thermosetting insulating adhesive is applied to the prepared lower opening peripheral surface 3b of the case 3, and the case 3 is placed on the upper surface of the capacitor substrate 2 so that the piezoelectric element 1 is positioned inside the recess 3a. Put it on. Thereafter, the case 3 or the capacitor substrate 2 is heated to cure the insulating adhesive by raising the temperature to 100 to 150 ° C., and the case 3 is bonded to the upper surface of the capacitor substrate 2. As a result, the piezoelectric resonator 10 is basically manufactured.

  In the next step, the input / output terminal electrode 2 f and the side ground electrode 6 a are formed on the side surface of the piezoelectric oscillator 10.

  For the input / output terminal electrode 2f and the side ground electrode 6a, a conductive resin paste in which metal powder is dispersed in a resin is prepared, and this conductive resin paste is used as a side surface of the piezoelectric oscillator 10 (on the capacitor substrate 2). It can be formed by applying the resin onto the side surface and the side surface of the case 3 using, for example, a screen printing method or a roller transfer method, and then curing the resin by heating or ultraviolet irradiation. Further, in the formation of the input / output terminal electrode 2f, the exposed portion where the extended portion 2d of the first capacitance electrode 2a and the second capacitance electrode 2b reaches the side surface of the second piezoelectric substrate 2c, the first mounting electrode 4 and the first mounting electrode 2f 2 The conductive resin paste is applied from the side surface of the second piezoelectric substrate 2c to the side surface of the case 3 so that the mounting electrode 5 covers the end portion reaching the side surface of the second piezoelectric substrate 2c, and the side ground electrode 6a In the formation, a conductive paste is applied from the side surface of the second piezoelectric substrate 2c to the side surface of the case 3 so that the ground electrode 6 covers the end portion reaching the side surface of the second piezoelectric substrate 2c.

  In addition, if the outer periphery of the opening peripheral surface 3b of the recess 3a on the lower side of the case 3 is positioned inside the outer periphery of the upper surface of the capacitor substrate 2, the first capacitor electrode 2a and the second capacitor electrode 2b Since the exposed part of the extension part 2d can be secured large, the electrical connection between the input / output terminal electrode 2f and the extension part 2d of the first capacitor electrode 2a and the extension part 2d of the second capacitor electrode 2b Can be stably connected.

  With respect to the piezoelectric resonator 10 thus obtained, the first capacitive electrode is set so that the first vibrating electrode 1a and the second vibrating electrode 1b of the piezoelectric resonator 10 of the present example manufactured by the above-described method have the same potential. The first capacitance is applied so that a voltage of the same potential is applied to 2a and the second capacitive electrode 2b and no potential difference is generated between the first vibrating electrode 1a and the second vibrating electrode 1b due to the voltage applied to the piezoelectric element 1. A potential difference is generated only between the electrode 2a and the second capacitor electrode 2b and the ground electrode 6, and the dielectric constant is changed by changing the degree of polarization of the piezoelectric material of the second piezoelectric substrate 2c. Further, by applying a voltage opposite to the voltage applied during the polarization process between the first capacitor electrode 2a and the second capacitor electrode 2b in the capacitor substrate 2 and the ground electrode 6, the polarization process is temporarily performed. The degree of polarization of the piezoelectric substrate performed can also be reduced. As described above, according to the piezoelectric oscillator of the present invention, after the assembly process, the capacitance of the capacitive substrate 2 is adjusted without affecting the characteristics of the piezoelectric element 1, and the oscillation frequency of the piezoelectric oscillator 10 is precisely adjusted. can do.

  It should be noted that the present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

  For example, in the above-described example of the piezoelectric oscillator of the present invention, the first capacitor electrode 2a and the second capacitor electrode 2b formed on the capacitor substrate 2, the first mounting electrode 4, the second mounting electrode 5, the ground electrode 6, and the input The output terminal electrode 2f and the side ground electrode 6a may be formed using a conductive resin having the same composition. In this case, the thermal expansion coefficients of the electrodes formed on one main surface and the other main surface of the capacitor substrate 2 are the same, so that each of the one main surface and the other main surface of the capacitor substrate 2 is the same. The difference in thermal expansion and contraction of the electrode is reduced, and the deformation of the capacitor substrate 2 can be reduced to prevent damage due to the thermal history.

  In the example of the piezoelectric oscillator of the present invention described above, the case 3 and the capacitor substrate 2 are bonded using an insulating adhesive, but may be bonded using a method that does not use an adhesive. For example, by using a resin having adhesiveness as the material of the case 3, a solvent capable of dissolving the opening peripheral surface 3 b of the case 3 is dropped on the entire opening peripheral surface 3 b so that the opening peripheral surface 3 b of the case 3 is formed. The case 3 can be bonded to the capacitor substrate 2 by this dissolved resin. In this case, the difference in thermal expansion and thermal contraction between the case 3 and the capacitor substrate 2 at the bonded portion is smaller than that in the case of bonding using an adhesive, and the case 3 is difficult to remove from the capacitor substrate 2.

  In addition, the capacitor substrate 2 has the first capacitor electrode 2a and the second capacitor electrode 2b arranged side by side on one main surface of the second piezoelectric substrate 2c and the second ground electrode 6b on the same main surface. A structure may be adopted in which the electrodes 2a and the second capacitor electrode 2b are arranged and deposited so as to form a capacitor between the gaps. In the case of such a structure, the piezoelectric element 1 and the ground electrode 6 do not overlap on the capacitor substrate 2, so that the first vibration electrode 1 a or the second vibration electrode 1 b of the piezoelectric element 1 and the ground electrode 6 are not connected. Therefore, the piezoelectric element 1 and the capacitor substrate 2 are less likely to affect each other, and the piezoelectric resonator 10 can be adjusted with high accuracy.

  As a method for connecting the piezoelectric element 1 and the capacitor substrate 2 in the piezoelectric resonator 10 of this example, the piezoelectric element 1 is stacked on the capacitor substrate 2 via the conductive connecting members 7a and 7b and electrically connected. However, the piezoelectric element 1 and the capacitor substrate 2 may be arranged at positions separated from each other on the mounting substrate and connected using wiring. When arranged in this way, a minute capacitance is not formed between the piezoelectric element 1 and the ground electrode 6, so that the influence exerted on each other between the piezoelectric element 1 and the capacitor substrate 2 is reduced. Therefore, the piezoelectric oscillator 10 capable of highly accurate frequency adjustment is obtained.

  In the above-described example of the piezoelectric oscillator of the present invention, the second piezoelectric substrate 2c is a piezoelectric substrate that is polarized in the thickness direction, the width direction, or the length direction at the stage of the collective substrate. After the capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6 are deposited, the first capacitor electrode 2a and the second capacitor electrode 2b are maintained while keeping the first capacitor electrode 2a and the second capacitor electrode 2b at the same potential. A voltage may be applied so as to generate a potential difference between the first capacitor electrode 2a and the ground electrode 6 and a polarization process may be partially performed only between the first capacitor electrode 2a and the second capacitor electrode 2b.

  In the above-described example of the piezoelectric oscillator of the present invention, the second piezoelectric substrate 2c is a piezoelectric substrate that is polarized in the thickness direction, the width direction, or the length direction at the stage of the collective substrate. After the piezoelectric element 1 is mounted on the first capacitor electrode 2, a voltage is applied so that a potential difference is generated between the first capacitor electrode 2 a and the second capacitor electrode 2 b of the capacitor substrate 2 and the ground electrode 6. Polarization may be partially applied only between 2a and the second capacitor electrode 2b.

  FIG. 9 is a sectional view showing another example of the embodiment of the piezoelectric oscillator of the present invention. In this example, only differences from the above-described embodiment of the piezoelectric resonator will be described, and the same components will be denoted by the same reference numerals and redundant description will be omitted.

  The capacitor substrate 22 of the piezoelectric resonator 20 of the example shown in FIG. 9 has a first capacitor electrode 2a, a ground electrode 6b, and a second capacitor electrode 2b arranged side by side on one main surface of the second piezoelectric substrate 2c. The capacitance formed between the first capacitor electrode 2a and the ground electrode 6b is formed near one main surface of the second piezoelectric substrate 2c existing between the electrodes, and the second capacitor electrode 2b and the ground electrode 6b. Is formed in the vicinity of one main surface of the second piezoelectric substrate 2c existing between the electrodes. The ground electrode 6b is connected to the side ground electrode 6a and is connected to the ground electrode 6 formed on the other main surface of the second piezoelectric substrate 2c.

  According to the piezoelectric oscillator 20 of the example shown in FIG. 9, the first capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6b can be deposited simultaneously in the same manufacturing process. Since the position between the two-capacitance electrode 2b and the ground electrode 6 is not displaced, the piezoelectric oscillator 20 capable of highly accurate frequency adjustment is obtained.

  Further, according to the piezoelectric resonator 20 of the example shown in FIG. 9, the first capacitor electrode 2a, the second capacitor electrode 2b, and the ground electrode 6b, which are attached to one main surface of the second piezoelectric substrate 2c, Even if the positions of the first mounting electrode 4, the second mounting electrode 5 and the ground electrode 6 deposited on the other main surface of the second piezoelectric substrate 2c are displaced, the first capacitance electrode 2a and the ground electrode 6 are disposed. The sum of the capacitance formed between the first mounting electrode 4 and the ground electrode 6b, and the capacitance formed between the second capacitance electrode 2b and the ground electrode 6 and the second mounting electrode 5, ground. The ratio with the sum of the capacitances formed between the electrodes 6b is always constant, and the capacitance can be adjusted relatively easily, so that the piezoelectric oscillator 20 capable of highly accurate frequency adjustment is obtained.

  FIG. 10 is a sectional view showing still another example of the embodiment of the piezoelectric oscillator of the present invention. In this example, only differences from the above-described embodiment of the piezoelectric oscillator will be described, and the same components will be denoted by the same reference numerals and redundant description will be omitted.

  In the example of the piezoelectric resonator 30 shown in FIG. 10, the second piezoelectric substrate 32c is formed by laminating two piezoelectric layers 32f and 32g, and the first capacitive electrode 2a attached to one main surface and the other. In a facing region S1 facing the ground electrode 6 deposited on the main surface, and a facing region S2 between the second capacitor electrode 2b deposited on one main surface and the ground electrode 6 deposited on the other main surface. The internal electrodes 32h electrically isolated from the other electrodes 2a, 2b, 6 are disposed between the piezoelectric layers 32f-32g, and the upper and lower piezoelectric layers 32f, 32g are separated from the internal electrodes 32h. The polarization direction is opposite in the vertical direction in the thickness direction of the piezoelectric layers 32f and 32g. For example, when the piezoelectric layer 32f is polarized upward in the thickness direction of the piezoelectric body 32f, the piezoelectric layer 32g is polarized downward in the thickness direction of the piezoelectric layer 32g.

  According to the piezoelectric resonator 30 of the example shown in FIG. 10, in each of the opposing regions S1 and S2, between the first capacitor electrode 2a and the ground electrode 6 and between the second capacitor electrode 2b and the ground electrode 6. Two capacitors each having the piezoelectric layers 32f and 32g as dielectric layers are connected in series, and the direction of the electric field in the two capacitors connected in series is the direction of the piezoelectric layers 32f and 32g. It is upward or downward in the thickness direction and is the same in the two capacitors. In addition, since the polarization directions of the piezoelectric layers 32f and 32g in the opposing regions S1 and S2 are reversed up and down in the thickness direction with the internal electrode 32h as a boundary, the first capacitor in the opposing regions S1 and S2 When a voltage is applied between the electrode 2a and the ground electrode 6 and between the second capacitor electrode 2b and the ground electrode 6, one of the upper and lower piezoelectric layers 32f and 32g with the internal electrode 32h as a boundary extends and the other Will shrink. For example, the piezoelectric layer 32f extends in the thickness direction of the piezoelectric layer 32f, and the piezoelectric layer 32g contracts in the thickness direction of the piezoelectric layer 32g. That is, the second piezoelectric substrate 32c when the voltage is applied between the first capacitor electrode 2a and the ground electrode 6 and between the second capacitor electrode 2b and the ground electrode 6 is the two layers of the second piezoelectric substrate 32c. When one of the piezoelectric layers 32f and 32g extends in the thickness direction, the other contracts in the thickness direction, and the amount of change in the thickness of each of the two piezoelectric layers 32f and 32g is canceled out. Specifically, since the change in thickness is small, it is possible to suppress the piezoelectric vibration that vibrates in the thickness direction of the second piezoelectric substrate 32c. Therefore, it is possible to suppress the generation of unnecessary peaks other than the desired frequency in the frequency-impedance characteristics due to the piezoelectric vibration of the second piezoelectric substrate 32c.

  Further, in the piezoelectric resonator 30 of the present example, the position of the ground electrode 6 overlaps with the gap region between the first capacitor electrode 2a and the second capacitor electrode 2b when the second piezoelectric substrate 32c is viewed in the thickness direction. It has become. For this reason, when the area of the ground electrode 6 cannot be increased due to mounting reasons or the like, it is difficult to increase the areas of the opposing regions S1 and S2. According to the piezoelectric resonator 30 of the present example, by arranging the internal electrode 32h having no restriction on the arrangement location in the piezoelectric layers 32f-32g, the area where the first capacitor electrode 2a and the internal electrode 32h face each other, the second Since the area where the capacitor electrode 2b and the internal electrode 32h face each other and the area where the ground electrode 6 and the internal electrode 32h face each other can be sufficiently secured, a large capacity can be obtained and the selection range of the capacity can be increased. The piezoelectric resonator 30 can be widened and the oscillation frequency can be easily set.

  In the piezoelectric oscillator 30 of the present example, the polarization directions of the upper and lower piezoelectric layers 32f and 32g need to be reversed with respect to the internal electrode 32h in at least the facing regions S1 and S2. In the entire second piezoelectric substrate 32c, the polarization directions of the upper and lower piezoelectric layers 32f and 32g may be reversed with respect to the piezoelectric layers 32f-32g. Further, in the structure shown in FIG. 10, the internal electrode 32h is formed integrally with the opposing regions S1 and S2 and wider than the opposing regions S1 and S2, but is separated into the opposing regions S1 and S2. It is also possible to adopt a configuration in which independent components are arranged.

  Such a second piezoelectric substrate 32c is obtained by, for example, producing the first piezoelectric substrate 1c and the second piezoelectric substrate 2c described above, and the polarization direction is opposite to that of the upper substrate as the piezoelectric layer 32f and the upper substrate. The lower substrate as the piezoelectric layer 32g is prepared, and the first capacitor electrode 2a and the second capacitor electrode 2b are deposited on the upper surface of the upper substrate, and the internal electrode 32h is formed on the upper surface of the lower substrate. The ground electrode 6, the first mounting electrode 4 and the second mounting electrode 5 are attached to the lower surface, the upper substrate and the lower substrate are bonded to each other through the prepreg, and the prepreg is cured by heating, whereby the piezoelectric layer It can be produced by integrating 32f and 32g.

  FIG. 11 is a cross-sectional view showing still another example of the embodiment of the piezoelectric oscillator of the present invention. In this example, only differences from the above-described embodiment of the piezoelectric oscillator will be described, and the same components will be denoted by the same reference numerals and redundant description will be omitted.

  In the piezoelectric resonator 40 of the example shown in FIG. 11, the ground electrode 6b is attached between the first capacitor electrode 2a and the second capacitor electrode 2b on one main surface of the second piezoelectric substrate 2c. The polarization direction of the second piezoelectric substrate 2c is such that the capacitance formation region S3 between the first capacitance electrode 2a and the ground electrode 6b and the capacitance formation region S4 between the second capacitance electrode 2b and the ground electrode 6b The direction is opposite in the direction parallel to the main surface. For example, in the capacitor forming region S3, the capacitor is polarized in a direction from the ground electrode 6b side to the first capacitor electrode 2a side in parallel to the main surface of the second piezoelectric substrate 2c, and in the capacitor forming region S4, the ground electrode 6b is parallel to the main surface. It is polarized in the direction from the side toward the second capacitor electrode 2b.

  According to the piezoelectric resonator 40 of the example shown in FIG. 11, the electric field directions between the first capacitor electrode 2a and the ground electrode 6b and between the second capacitor electrode 2b and the ground electrode 6b are the same. For example, an electric field is applied in a direction from the first capacitance electrode 2a to the second capacitance electrode 2b in parallel with the main surface of the second piezoelectric substrate 2c. In addition, since the polarization direction of the second piezoelectric substrate 2c in the capacitance formation regions S3 and S4 is reversed in the direction parallel to the main surface of the second piezoelectric substrate 2c, the first capacitance in the capacitance formation regions S3 and S4. When a potential difference is generated between the electrode 2a and the second capacitor electrode 2b, one of the capacitor formation regions S3 and S4 is expanded and the other is contracted. For example, when the polarization direction of the capacitance forming region S3 and the direction of the electric field are the same, and the polarization direction of the capacitance forming region S4 and the direction of the electric field are opposite to each other, the capacitance forming region S3 is formed on the second piezoelectric substrate 2c. The capacitor forming region S4 extends in a direction parallel to the main surface, and contracts in a direction parallel to the main surface of the second piezoelectric substrate 2c. That is, when a voltage is applied between the first capacitor electrode 2a and the second capacitor electrode 2b, the second piezoelectric substrate 2c has a polarization direction and an electric field in the capacitor formation region S3 and the capacitor formation region S4 as described above. Extends in the direction parallel to the main surface of the second piezoelectric substrate 2c on the side where the direction of the electrode is the same, and parallel to the main surface of the second piezoelectric substrate 2c on the side where the polarization direction and the direction of the electric field are opposite. Therefore, the amount of change in each polarization direction is canceled out and the change is reduced as a whole. Therefore, the piezoelectric vibration in the direction parallel to the main surface of the second piezoelectric substrate 2c can be reduced. Therefore, it is possible to suppress the generation of unnecessary peaks other than the desired frequency in the frequency-impedance characteristics due to the piezoelectric vibration of the second piezoelectric substrate 2c.

  As the capacitor substrate 42 in the example shown in FIG. 11, the length of the second piezoelectric substrate 2c is 3.2 mm, the width is 1.2 mm, the thickness is 0.3 mm, and the distance between the ground electrode 6b and the first capacitor electrode 2a and A capacitor substrate 42 was prepared in which the distance between the ground electrode 6b and the second capacitor electrode 2b was 0.2 mm, and the distance between the ground electrode 6 formed on the lower surface, the first mounting electrode 4 and the second mounting electrode 5 was 0.8 mm. Measurements were made. The first mounting electrode 4 and the second mounting electrode 5 were grounded, and a 0.75 kV DC voltage (polarization voltage) was applied to the ground electrode 6b at 25 ° C. for 20 seconds for polarization. Thereafter, frequency-impedance characteristics were measured using an impedance analyzer. FIG. 12 is a graph showing the impedance waveform of only the second piezoelectric substrate 2c. The curve drawn by the graph was smooth, and it was confirmed that the generation of unnecessary peaks due to resonance was effectively suppressed.

  In the piezoelectric resonator 40 of this example, the ground electrode 6b is attached between the first capacitor electrode 2a and the second capacitor electrode 2b on one main surface of the second piezoelectric substrate 2c. By increasing the area of the ground electrode 6b, the distance (gap) between the first capacitor electrode 2a and the ground electrode 2b and between the second capacitor electrode 2b and the ground electrode 6b can be reduced. Therefore, when the area of the ground electrode 6b is increased, the interval (gap) between the first capacitor electrode 2a and the ground electrode 6b and the interval (gap) between the second capacitor electrode 2b and the ground electrode 6b are reduced. Therefore, a large capacity can be obtained, the capacity selection range is widened, and the piezoelectric oscillator 40 in which the oscillation frequency can be easily set can be obtained.

  Further, when the space between the first capacitor electrode 2a and the ground electrode 2b and the interval between the second capacitor electrode 2b and the ground electrode 6b are covered with resin, the space between the first capacitor electrode 2a and the ground electrode 2b is used. Between the second capacitor electrode 2b and the ground electrode 6b can be prevented.

  In such a second piezoelectric substrate 2c, the ground electrode 6b is deposited between the first capacitive electrode 2a and the second capacitive electrode 2b on one main surface of the second piezoelectric substrate 2c, and then the first capacitive electrode. 2a and the second capacitor electrode 2b are set to the same potential, and a voltage is applied between these electrodes and the ground electrode 6b, so that the polarization direction of the second piezoelectric substrate 2c changes between the first capacitor electrode 2a and the ground electrode 6b. It is produced by performing polarization so that the capacitance forming region S3 between and the capacitance forming region S4 between the second capacitor electrode 2b and the ground electrode 6b are reversed.

  A sample of the piezoelectric oscillator 10 of the example shown in FIG. 1 was prepared as the piezoelectric oscillator of the present invention, and the dependency of the oscillation frequency on the polarization voltage was measured.

  The piezoelectric element 1 is a thickness-sliding vibration mode in which lead titanate is a main component, polarized in the long side direction of a rectangular parallelepiped first piezoelectric substrate 1c having a length of 1.0 mm, a width of 0.2 mm, and a thickness of 40 μm. The energy confinement type piezoelectric element 1 using the fundamental wave of is used. In addition, as the case 3, an insulating resin in which silicon dioxide powder as an inorganic filler occupying 80% by mass of the epoxy resin and alumina silicate glass powder occupying 3% by mass in the epoxy resin is dispersed by injection molding. By doing so, it was processed as a collective case member provided with a plurality of recesses 3a on the lower side.

  As the capacity substrate 2, a collective substrate is prepared which takes a large number of rectangular flat plates having a length of 0.6 mm, a width of 0.5 mm, and a thickness of 0.05 mm, which are mainly composed of lead zirconate titanate, The first capacitor electrode 2a and the second capacitor electrode 2b are attached to the upper surface and the first mounting electrode 4 is applied to the lower surface by using a conductive resin in which silver powder occupying 85% by mass of the whole is dispersed in the epoxy resin. The second mounting electrode 5 and the ground electrode 6 were deposited. Further, the thicknesses of the first capacitor electrode 2a and the second capacitor electrode 2b on the upper surface of the capacitor substrate 2 were formed with a target value of 15 μm. In the polarization treatment, the first capacitor electrode 2a and the second capacitor electrode 2b are grounded and the polarization voltage is applied to the ground electrode 6 under the conditions of a DC voltage of 1.5 kV / mm at 25 ° C. and a voltage application time of 30 minutes. Thus, a potential difference was generated between the ground electrode 6 and the first capacitor electrode 2a and between the ground electrode 6 and the second capacitor electrode 2b. In the following description, the direction in which the polarization voltage is applied is a direction from the ground electrode 6 toward the first capacitor electrode 2a and the second capacitor electrode 2b, and a direction from the first capacitor electrode 2a and the second capacitor electrode 2b toward the ground electrode 6. Is the reverse direction.

  Disposed on each first capacitor electrode 2a and second capacitor electrode 2b on the upper surface of the prepared capacitor substrate 2 are conductive connection members 7a and 7b in which silver powder occupying 80% by mass of the whole is dispersed in silicone resin. The piezoelectric element 1 was mounted on the capacitor substrate 2 by placing the piezoelectric element 1 thereon and then curing the conductive connecting members 7a and 7b. As a result, the conductive connecting members 7a and 7b ensure a height that does not hinder the vibration of the mounted piezoelectric element 1. Next, an insulating adhesive made of epoxy resin is applied to the lower peripheral edge surface 3b of the case 3, and the case 3 is placed on the capacitor substrate 2 so that each piezoelectric element 1 is positioned inside the corresponding recess 3a. Then, the insulating adhesive was cured by pressing the case 3 downward at 0.2 MPa for 40 minutes while heating to 160 ° C. while being heated to 160 ° C.

  The joined collective case member and the collective capacitor substrate are cut into individual piezoelectric oscillators 10 using a dicing saw along the boundaries of the piezoelectric oscillators 10, and the exposed side surfaces of the piezoelectric oscillators 10 are cut off. By forming the input / output terminal electrode 2f and the side ground electrode 6a, a sample of the piezoelectric resonator of the present invention was manufactured.

  Regarding the sample of the piezoelectric oscillator of the present invention manufactured by the above method, the first capacitor electrode 2a and the second capacitor electrode 2b are grounded while the first capacitor electrode 2a and the second capacitor electrode 2b are grounded in a finished product state. First, a DC voltage of −1.5 kV / mm to +2.5 kV / mm is applied between the electrode and the ground electrode 6 under the conditions of 25 ° C. and a voltage application time of 1 second each, and the second piezoelectric substrate of the capacitance forming portion 2e When the polarization process is performed on 2c, the change in the capacitance value with respect to the polarization voltage of the capacitance substrate 2, the rate of change in the oscillation frequency of the piezoelectric resonator 10 with respect to the capacitance value of the capacitance substrate 2, and the resulting capacitance substrate 2 The measurement results of the frequency change rate of the oscillation frequency of the piezoelectric resonator 10 with respect to the polarization voltage are shown in the diagrams of FIGS. 6, 7 and 8, respectively. At this time, since the polarization voltage of the same potential was applied to the first vibrating electrode 1a and the second vibrating electrode 1b, no change was observed in the polarizability of the piezoelectric element 1.

  FIG. 6 is a diagram showing a change in the capacitance value of the capacitive substrate 2 due to the application of the polarization voltage. The horizontal axis represents the applied polarization voltage (unit: kV / mm), the vertical axis represents the capacitance value (unit: pF) of the capacitive substrate 2, and the characteristic curve represents the change in the capacitance value of the capacitive substrate 2 with the application of the polarization voltage. The state of is shown. As can be seen from the results shown in FIG. 6, by changing the polarization voltage, the magnitude of the voltage (corresponding to the potential difference between the first capacitor electrode 2a and the second capacitor electrode 2b and the ground electrode 6) is changed. It can be seen that the capacitance value of the capacitance substrate 2 changes.

  Next, FIG. 7 shows the change in the capacitance value of the capacitor substrate 2 and the frequency change rate of the piezoelectric resonator 10 of this embodiment (ratio of the difference between the changed oscillation frequency and the original oscillation frequency with respect to the original oscillation frequency). It is a diagram which shows the relationship of these. The horizontal axis represents the capacitance value (unit: pF) of the capacitive substrate 2 changed by applying the polarization voltage, the vertical axis represents the frequency change rate (unit:%), and the characteristic curve represents the change in the capacitance value of the capacitive substrate 2. The state of the change of the frequency change rate accompanying with is shown. As can be seen from the results shown in FIG. 7, it can be seen that the frequency change rate of the piezoelectric oscillator 10 is changed by changing the capacitance value of the capacitive substrate 2 by changing the polarization voltage.

  FIG. 8 is a diagram showing changes in the frequency change rate of the oscillation frequency due to the application of the polarization voltage. The horizontal axis represents the applied polarization voltage (unit: kV / mm), the vertical axis represents the frequency change rate (unit:%) of the oscillation frequency of the piezoelectric resonator 10, and the characteristic curve represents the frequency change rate with application of the polarization voltage. The state of change is shown. As can be seen from the results shown in FIG. 8, by changing the polarization voltage applied to the capacitor substrate 2, the frequency change rate changes accordingly, and the oscillation frequency of the piezoelectric oscillator 10 changes. I understand.

  In summary, since the piezoelectric resonator 10 of this example has the piezoelectric element 1 mounted on the capacitive substrate 2 subjected to the polarization treatment, the capacitance value of the capacitive substrate 2 is set by applying a negative polarization voltage. It is possible to slightly reduce the oscillation frequency of the piezoelectric oscillator 10 by slightly increasing the oscillation frequency of the piezoelectric oscillator 10 and applying a positive polarization voltage to increase the capacitance value of the capacitor substrate 2. Yes.

  That is, it is possible to increase or decrease the oscillation frequency of the piezoelectric oscillator 10 by applying a polarization voltage to the capacitive substrate 2 of the piezoelectric oscillator 10 in the finished product state. The oscillation frequency can be finely adjusted.

  From the above results, according to the piezoelectric resonator 10 of the present invention, the first vibrating electrode 1a and the second vibrating electrode 1b facing each other with the first piezoelectric substrate 1c sandwiched between the surfaces of the first piezoelectric substrate 1c are attached. The first capacitor electrode 2a and the second capacitor electrode 2b are respectively attached to one main surface of the piezoelectric element 1 and the second piezoelectric substrate 2c, and the first capacitor electrode 2a and the second capacitor are mounted on the other main surface. A capacitor substrate 2 on which a ground electrode 6 for forming a capacitor with the electrode 2b is attached, and the piezoelectric element 1 is arranged on the capacitor substrate 2 with a space for vibration around it. Since the first capacitor electrode 2a and the first vibrating electrode 1a and the second capacitor electrode 2b and the second vibrating electrode 1b are electrically connected to each other, the input side terminal of the piezoelectric element 1 ( First vibrating electrode 1a) and output side terminal (second vibrating electrode 1b) Is a voltage for changing the polarizability of the capacitance forming portion 2e of the second piezoelectric substrate 2c between the first capacitance electrode 2a and the second capacitance electrode 2b of the capacitance substrate 2 and the ground electrode 6 Therefore, a voltage that generates a potential difference is not applied between the first vibrating electrode 1a and the second vibrating electrode 1b, and the capacitance substrate is not affected without affecting the degree of polarization of the piezoelectric material of the piezoelectric element 1. Voltage is applied so as to generate a potential difference only in the capacitance forming portion 2e in which the first capacitance electrode 2a and the second capacitance electrode 2b in FIG. It becomes possible to change the degree of polarization of the piezoelectric material.

  In addition, since the piezoelectric element 1 and the capacitor substrate 2 are configured as separate substrates, a voltage is applied to the capacitor substrate 2 without affecting the piezoelectric element 1, and the piezoelectric material of the second piezoelectric substrate 2c is not affected. It is possible to change the degree of polarization.

  Therefore, the capacitance value can be changed by changing the dielectric constant of the capacitance forming portion 2e by changing the degree of polarization of the piezoelectric material of the capacitance forming portion 2e, which allows precise frequency adjustment in the state of the finished product. I was able to confirm that it was possible.

It is an external appearance perspective view which shows an example of embodiment of the piezoelectric oscillator of this invention. FIG. 2 is a cross-sectional view of the piezoelectric resonator of FIG. 1 taken along the line A-A ′. (A) is the external appearance perspective view which looked at the case of the piezoelectric oscillator of FIG. 1 from the downward direction, (b) is the external appearance perspective view of the state which removed the case of the piezoelectric oscillator of FIG. It is an equivalent circuit diagram of an example of an embodiment of a piezoelectric oscillator of the present invention. FIG. 2 is a cross-sectional view taken along line B-B ′ of the piezoelectric resonator in FIG. 1. It is a diagram which shows the change of the capacitance value of a capacity | capacitance board | substrate by the application of the polarization voltage to a capacity | capacitance board | substrate. It is a diagram which shows the change of the frequency change rate by the change of the capacitance value of a capacity | capacitance board | substrate. It is a diagram which shows the change of the frequency change rate by application of a polarization voltage. It is sectional drawing which shows the other example of embodiment of the piezoelectric oscillator of this invention. It is sectional drawing which shows the further another example of embodiment of the piezoelectric oscillator of this invention. It is sectional drawing which shows the further another example of embodiment of the piezoelectric oscillator of this invention. It is a diagram which shows the impedance change by the change of the frequency of a capacity | capacitance board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element 1a ... 1st vibration electrode 1b ... 2nd vibration electrode 1c ... 1st piezoelectric substrate 2, 32, 42 ... Capacitance substrate 2a ... 1st capacitance electrode 2b. ..Second capacitance electrodes 2c, 32c ... second piezoelectric substrate
32f, 32g ... piezoelectric layer 2d ... extension part 2e ... capacitor formation part 2f ... input / output terminal electrode 3 ... case 3a ... concave part 3b ... periphery peripheral surface 4. ..First mounting electrode 5 ... second mounting electrode 6,6b ... ground electrode 6a ... side ground electrode 7a, 7b ... conductive connecting material
10, 20, 30, 40 ... Piezoelectric oscillator
32h ... internal electrode

Claims (7)

A piezoelectric element formed by attaching a first vibrating electrode and a second vibrating electrode facing each other across the surface of the first piezoelectric substrate across the first piezoelectric substrate;
A first capacitance electrode and a second capacitance electrode are respectively deposited on one main surface of the second piezoelectric substrate, and a capacitance is provided between the first capacitance electrode and the second capacitance electrode on one or the other main surface. A capacitor substrate on which a ground electrode to be formed is attached;
The piezoelectric element is disposed with respect to the capacitive substrate while securing a space for vibration around the capacitive substrate, the first capacitive electrode and the first vibrating electrode, and the second capacitive electrode and the second vibrating electrode. Each electrode is electrically connected ,
The piezoelectric oscillator of the second piezoelectric substrate between the first capacitor electrode and the second capacitor electrode and the ground electrode is characterized that you have been capacitor is polarized is formed. 2. The piezoelectric device according to claim 1, wherein the ground electrode is attached to the other main surface of the second piezoelectric substrate so as to face the first capacitor electrode and the second capacitor electrode. Oscillator. 2. The piezoelectric resonator according to claim 1, wherein the piezoelectric element is mounted on one main surface of the capacitive substrate via a conductive connecting material. A first mounting electrode electrically connected to the first capacitor electrode and a second mounting electrode electrically connected to the second capacitor electrode are attached to the other main surface of the second piezoelectric substrate. The piezoelectric resonator according to claim 1, wherein: 4. The piezoelectric oscillator according to claim 3, wherein the first piezoelectric substrate and the second piezoelectric substrate are made of the same ferroelectric material. The second piezoelectric substrate is formed by laminating two piezoelectric layers, a region facing the first capacitive electrode and the ground electrode deposited on the other main surface, and the second capacitive electrode and the other capacitive electrode. An internal electrode electrically isolated between the piezoelectric layers is disposed in a region facing the ground electrode deposited on the main surface, and polarization of the upper and lower piezoelectric layers with the internal electrode as a boundary The piezoelectric resonator according to claim 1, wherein the direction is reverse. The ground electrode is attached between the first capacitor electrode and the second capacitor electrode on one main surface of the second piezoelectric substrate, and a polarization direction of the second piezoelectric substrate is set to the first piezoelectric substrate. 2. The piezoelectric resonator according to claim 1, wherein the piezoelectric oscillator is in a reverse direction between the capacitor electrode and the ground electrode and between the second capacitor electrode and the ground electrode.

Images